Identifier

Author

Degree

Doctor of Philosophy (PhD)

Department

Plant, Environmental Management and Soil Sciences

Document Type

Dissertation

Abstract

Under Louisiana climatic conditions, production of sugarcane (Saccharum spp.) is limited to a maximum growth period of nine months. To increase sucrose concentration in the crop, ripener is applied prior to harvest. The chemical ripeners, glyphosate and trinexapac-ethyl were applied to the sugarcane cultivars HoCP 96-540, L 99-226, L 99-233, HoCP 00-950, and L 01-283 eight weeks prior to harvest. When glyphosate was applied at 210 g ae/ha, TRS for the cultivars was increased 10 to 28% compared with the nontreated. Increases in TRS with glyphosate were greatest for HoCP 96-540 and L 99-226 and least for HoCP 00-950 and L 01-283. Trinexapac-ethyl at 350 g ai/ha increased TRS for the cultivars 7 to 10% and increases were greatest for L 99-233 and least for HoCP 00-950. Sugarcane yield averaged across cultivars was reduced 9% with glyphosate and 7% for trinexapac-ethyl at 350 g/ha. An increase in sugar yield per hectare, a function of TRS and sugarcane yield, was observed only when glyphosate was applied to HoCP 96-540 (16% increase) and when trinexapac-ethyl at 300 g ai/ha was applied to L 01-283 (13% increase). In a second study where eight cultivars were harvested six weeks after glyphosate application, TRS for HoCP 96-540 was increased an average of 10% compared with the nontreated and sugarcane yield was decreased 17%; sugar yield was not affected. In another study, sugarcane yield, TRS, and sugar yield were not affected by nitrogen rates of 67, 112, and 157 kg/ha. Six weeks after application of glyphosate at 210 g/ha TRS averaged across N rates was 11% greater than the nontreated and 9% greater than when trinexapac-ethyl was applied at 350 g/ha. TRS following trinexapac-ethyl was equivalent to the nontreated. Sugarcane yield and sugar yield were not affected by ripener application. In a separate study TRS and sugar yield were not affected when glyphosate or trinexapac-ethyl was applied in 75 and 150 L/ha spray volume or when none or 0.25% v/v surfactant was added to the spray solution. Averaged across spray volume and surfactant treatments, TRS was as much as 8% greater for glyphosate compared with trinexapac-ethyl.